The present invention relates to a steam generator having a stationary fluidized-bed hearth.
Such a steam generator is known from the journal, Chemie-Ingenieur Technik 51, (1979), No. 3, p. 188. Using this steam generator it is basically possible to run part loads, since individual sections of the fluidized bed can be cut in or out. The known steam generator is arranged as a multi-flue boiler. Some of the sections are provided with evaporator heating surfaces, whereas the remainder are provided with evaporator and intermediate superheater heating surfaces. This boiler configuration makes partial-load control more difficult.
In addition, a steam generator with a fluidized-bed hearth is also known (journal VDI report No. 322, 1978, p. 10), in which coal is supplied evenly by belt-charging machines. The unburned coal particles that are carried off the fluidized bed are subsequently burned above the fluidized bed with the help of secondary air. In this steam generator, the fluidized bed is not divided into sections. The performance of the furnace is controlled by the quantity of combustion air that is used.
Finally, it is known that in fluidized-bed hearths the flue dust carried off by the flue gas is removed and fed back to the fluidized bed.